The module uses a genuine quality relay with normally open interface. Maximum load: AC 250V/10A, DC 30V/10A. Uses SMD optocoupler isolation for strong drive capability and stable performance; trigger current is 5mA. Features a power indicator (green) and relay status indicator (red). User-friendly interface with all connections accessible via direct connection terminals for maximum convenience. Module Operating Voltage: 9V Color: Red Material: Metal Module Size: 73mm x 50mm x 18.5mm (L x W x H) Module Interface: 1. DC +: Positive power supply (VCC) 2. DC-: Power supply negative (GND) 3. IN1, IN2, IN3, IN4: Can control the relay with a high or low level signal. S1, S2, S3, S4: SET HIGH OR LOW LEVEL Relay Outputs: 1. NO1,2,3,4: Normally open relay interface 2. COM1,2,3,4: Common relay interface 3. NC1,2,3,4: Normally closed relay interface High and Low Level Trigger: Trigger with a low level when the jumper connects to LOW. Trigger with a high level when the jumper connects to HIGH. Package: 1 * 4CH Relay Module (Only the above package content is included; other products are not.) Note: Light photography and different displays may cause the color of the item in the picture to be slightly different from the real thing. The allowed measurement error is +/- 1-3 cm.